Architectural fabrics are finding increasing use in roofing and side panels for public facilities such as airports and sports arenas, and functional decorative elements such as awnings, tents and canopies. These fabrics offer advantages compared to traditional materials because of modern appearance, ease of construction, rapid fabrication and lower cost. Architectural fabrics typically comprise a reinforcing cloth for strength and a polymeric coating to render the cloth weatherproof. The cloth may be made from a variety of materials such as cotton, nylon, polyester, polyolefin or glass, or blends of such fibers. The cloth may be woven as commonly done with cotton, nylon or glass, or it may be non-woven as with fabrics sold under the trademarks TYVEK®, TYPAR® and REEMAY®. The TYVEK® trademark is used by the DuPont Company for flash-spun polyethylene fabrics, and the TYPAR® and REEMAY® trademarks are used by Reemay, Inc. for spunbonded polypropylene and polyester fabrics, respectively. The polymeric coating may comprise any resin resistant to weathering conditions including fluoropolymers, vinyl, acrylics, natural or synthetic rubber. Of these, fluoropolymers are especially preferred because of their extreme resistance to a broad range of weathering conditions. Vinyl coated polyester cloth finds extensive use in awnings and tents because of its low cost. It offers excellent resistance to rain, however, on exposure to sunlight the vinyl deteriorates eventually leading to discoloration and failure of the fabric.
The useful lifetime of a vinyl coated fabric can be markedly extended by laminating a thin overlayer of a fluoropolymer such as polyvinyl fluoride to the weather-side of the vinyl coated fabric. If the fluoropolymer is pigmented or contains an additive that highly absorbs ultraviolet light, sunlight is effectively blocked from the underlying vinyl and its lifetime is greatly extended. Although this extends the usefulness of the fabric, in some cases like sports arenas, it is desired for the lifetime of the fabric to be even longer than can be provided by typical fabric containing vinyl resin. In these applications, extremely durable materials like glass cloth and perfluorinated resins like polytetrafluoroethylene (PTFE) or copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) or perfluoro(alkyl vinyl ethers) (PAVE) may be chosen. In all of these fabrics, the outer exposed surface of the fabric has a fluoropolymer coating.
In the use of architectural fabrics, it is frequently necessary to seam sections of the fabric together to provide a covering large enough to enclose an opening in, or in some cases, to cover the entire structure. Butt seams are formed by bringing the edges of two coated fabric pieces together and applying a reinforced tape to the underside of the seam. The reinforcing tape may be heat sealed to the fabric pieces completing the seam. There is always a narrow gap between the edges forming the butt seam, which collects dirt and debris resulting in an aesthetically compromised structure. Lap seams are formed by overlapping two pieces of coated fabric and heat sealing them together. In this case, fabric edges collect dirt and debris. A seam sealant that is easily applied to fill the gaps in butt seams or smooth the edges of lap seams is needed to prevent these areas from collecting dirt and becoming unsightly. For architectural fabrics with a fluoropolymer surface, effective seam-sealants are not presently available because the excellent release properties of the fluoropolymer surface prevent adequate adhesion of known available sealants to the coated fabric. A seam sealant suitable for materials with a fluoropolymer coating on their surface would be useful in other applications as well, such as fluoropolymers sheet materials for conveyor belts or release sheets, especially in the food industry or the precision manufacture of electronic components where debris free environments are important.